The present disclosure relates generally to medical devices and, more particularly, to optical medical sensors used for sensing physiological characteristics of a patient.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of medicine, doctors frequently desire to monitor certain physiological characteristics of their patients. Accordingly, a wide variety of devices have been developed for monitoring many such physiological characteristics. These devices provide doctors and other healthcare personnel with the information they need to provide the best possible healthcare for their patients. As a result, such monitoring devices have become an indispensable part of modern medicine.
One technique for monitoring certain physiological characteristics of a patient is commonly referred to as pulse oximetry, and the devices built based upon pulse oximetry techniques are commonly referred to as pulse oximeters. Pulse oximetry may be used to non-invasively measure various blood flow characteristics, such as the blood-oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsations supplying patient tissue, and/or the rate of blood pulsations corresponding to each heartbeat of a patient. In fact, the “pulse” in pulse oximetry refers to the time varying amount of arterial blood in the tissue during each cardiac cycle.
Pulse oximeters typically utilize an emitter to transmit light through a patient's tissue, toward a detector that photoelectrically detects the amount of light that has been lost due to absorption and/or scattering by the tissue. Based upon the amount of light absorbed or scattered, one or more of the above physiological characteristics may be calculated. Light passed through the tissue is typically selected to be of one or more wavelengths that may be absorbed or scattered by the patient's blood to a degree that correlates with the amount of a particular blood constituent present in the blood. Therefore, the amount of light absorbed and/or scattered may then be used to estimate the amount of blood constituent in the tissue using various algorithms.
Pulse oximeter sensors typically are placed in a certain position on a patient. For the sensor to operate properly, this position must be maintained. Small changes in the conformation of the sensor may cause the optical components to lose their contact with the skin, resulting in changes to the emitted and/or detected light, which in turn may lead to signal artifacts. Additionally, the photodetector should be oriented in such a way to receive a clear signal from the emitter despite potential transmission barriers (e.g., bone) in the tissue. Since it may prove difficult to constantly maintain emitter and photodetector positioning for a sensor attached to a moving patient, it may be beneficial to employ multiple photodetectors and/or emitters on a single sensor such that the probability of obtaining a good physiological measurement at a given time may be improved.
However, while using an array of photodetectors may address the aforementioned issues, it also introduces new challenges. For example, if every photodetector in the photodetector array were to possess a dedicated line to the monitor, the cable required to couple a sensor having a large number of photodetectors to a monitor would quickly become impractical, especially since the size and weight of the cable might tend to dislodge the sensor from its position on the patient's body. Additionally, the manufacturing cost and the likelihood of manufacturing defects would also be expected to increase with the increasing number of communication lines that would be coupled to the sensor, traverse the length of the cable, and be properly coupled to the monitor for the system to be operational.